Many rodent and similar species have been domesticated and are now
kept as pets. Some species, like the Norway rat and house mouse,
began their association with humans as commensals, living in
our houses and farms and cities for centuries before being actively
domesticated by humans in recent times. Other species entered
domestication millennia or centuries ago: humans first domesticated
the guinea pig three thousand years ago, Romans kept rabbits a
thousand years ago. Over the nineteenth and twentieth century, many
more species were taken directly from the wild and started down the
path of domestication, from the Norway rat in the 19th century and
the Syrian hamster in the early part of the 20th, to recent arrivals
such as the dwarf hamster and prairie dog.

Pet rodent
taxonomy

How are all these species related to each other? The table below
summarizes the classification of the most common rodent species kept
as pets. Two additional species, the domestic rabbit and the sugar
glider, are not rodents at all. Domestic rabbits are
Lagomorphs, a separate order of placental mammals (Eutheria),
and sugar gliders are marsupials in the orderDiprotodontia.

Taxonomy is a living branch of science, and new discoveries are
made frequently in areas like molecular analysis, fossil finds,
comparative anatomical studies, and hybridization studies. These new
findings lead taxonomists to modify the classification of various
animal groups. Hence, some classifications are under debate as
taxonomists weigh the competing and sometimes conflicting evidence
for degrees of relatedness between species (and the debates can get
quite heated!). I have included some of these debates in the
notes section below.

Disclaimer: this classification is for casual interest only.
For the most reliable source of nomenclature and classification,
consult the relevant scientific literature.

(1) The old classification within the order Rodentia used to
include three suborders: (a) Sciuromorpha (squirrel-like rodents),
(b) Myomorpha (rat-like rodents), and (c) Hystricomorpha
(porcupine-like rodents). These three terms are still frequently
used. However, the new classification recognizes only two
suborders: Sciurognathi and Hystricognathi. The old suborders
Sciuromorpha and Myomorpha basically combine to become infraorders
of Sciurognathi, with two families of Sciuromorpha (Geomyidae and
Heteromyidae) switching into Myomorpha. The Hystricomorpha fall
entirely under Hystricognathi, with division between New and Old
world groups (see Walker's Mammals of the World: Rodentia
page)

(2) The superfamily Muroidea is essentially the same group as
suborder Myomorpha except that it excludes Dipodidae
family (51 species including birch mice, jumping mice, and
jerboas).

(3) There is some molecular evidence that spiny mice
(Acomys spp.) may be more closely related to gerbils
(Gerbillinae) than to true mice (Murinae) (Chevet et al.
1993).

(4) Egyptian spiny mouse and Arabian spiny mouse are sometimes
considered the same species (Acomys cahirinus) but
different subspecies (Egyptian as A. c. cahirinus and
Arabian as A. c. dimiditus), with A. c. cahirinus
being the commensal form of A. c. dimiditus. Sometimes
different species (Egyptian as A. cahirinus and Arabian as
A. dimiditus).

(5) Sometimes, the family called Cricetidae (includes
Cricetinae and Gerbilinae as well as some other groups) is
considered a separate family within Muroidea, like Muridae. But
more modern classifications lump Cricetidae within Muridae
(ref).

(6) Campbell's dwarf hamster and Winter White hamster
sometimes considered same species (Phodopus sungorus) but
different subspecies (Campbell's as P. s. campbelli and
Winter White as P. s. sungorus), and sometimes considered
different species (Campbell's as P. campbelli and Winter
White as P. sungorus).

(7) The Chinese hamster and Chinese striped hamster are
sometimes considered the same species (Cricetulus griseus)
but different subspecies (Chinese striped hamster as C. g.
barabensis), sometimes considered different species (Chinese
hamster: Cricetulus griseus and Chinese striped hamster:
Cricetulus barabensis) (ref).

(8) There is some question about whether guinea pigs aren't
rodents at all, but a separate group, and their current suborder
Caviomorpha should be given order status on par with Rodentia (Li
et al. 1992).